Objective Atrial functional mitral regurgitation (A-FMR) has been suggested as a new aetiology of functional MR (MR); however, its prognosis and prognostic predictors are not fully elucidated. Aim of this study was to investigate the prognosis and prognostic predictors of A-FMR in comparison with ventricular functional MR (V-FMR). Methods Three hundred and seventy-eight consecutive patients with moderate-to-severe or severe functional MR were studied. Functional MR was classified into V-FMR (N=288) and A-FMR (N=90) depending on the alterations of left ventricle (LV) or left atrium (LA) along with clinical context and diagnosis of ischaemic heart disease or cardiomyopathy. Results During a median follow-up of 4.1 (2.0-6.7) years, all-cause mortality, cardiovascular mortality and heart failure (HF) hospitalisation occurred in 98 (26%), 81 (21%) and 177 (47%) patients, respectively, and rates of these events and the composite end point of all-cause mortality and HF hospitalisation were consistently higher in V-FMR than A-FMR (unadjusted HR 1.762 (95% CI 1.250 to 2.438), p<0.001; adjusted HR 1.654 (95% CI 1.027 to 2.664), p=0.038, for the composite end point). Further analysis showed different prognostic predictors between V-FMR and A-FMR; while age and LA volume index were independent prognostic predictors of both V-FMR and A-FMR, systolic blood pressure and B-type natriuretic peptide were also those of V-FMR, and estimated glomerular filtration rate, LV end-systolic dimension and tricuspid regurgitation were also those of A-FMR. Conclusions The prognosis of V-FMR was significantly worse than that of A-FMR, and prognostic predictors were different between V-FMR and A-FMR. Our study suggests the importance of discriminating A-FMR and V-FMR, and that different treatment strategies may be considered for each aetiology.
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